Classıfıcatıon of ımpressıon technıques ın complete dentures,personal trays and border molding_fc8e86eab3c0d11748f2d406a8e0d23b
Classification of Impression Techniques in Complete Dentures
Page 1
Asist. Prof. Dr. Fulya GÜLENER
Biruni University, Faculty of Dentistry, Department of Prosthetic Dentistry
Page 2: Complete Denture Impression
A good impression is the foundation for creating a complete denture.
Definition: A complete denture impression is a negative registration of the entire denture bearing area, including stabilizing and border seal areas in an edentulous mouth.
Page 3: Principles of Impression Making
The impression should capture the entire basal seat.
The border must conform to the anatomical and physiological limits of the structures.
Space must be available for the final impression material within the tray.
Perform a physiological type of border molding procedure (under dentist’s guidance).
Selective pressure must be applied to the basal seat during impression making.
The impression must be removed without injuring the mucous membrane.
A guiding mechanism should assist in the correct positioning of the tray.
The tray and impression material must be dimensionally stable.
External shape should resemble the external form of the complete denture.
Page 4: Factors in Impression Stage
Two crucial factors in the impression process are:
Impression Material
Impression Trays
The impression for complete dentures is generally taken in two steps:
Preliminary Impression
Functional Impression
Page 5: Preliminary (Primary) Impression
Purposes:
Diagnosis
Construction of custom impression trays for functional impressions
Must capture 3-D contours of intraoral landmarks (e.g., retromolar pads, retromylohyoid space).
An accurate preliminary cast facilitates quality final impressions by recording all anatomical landmarks.
Page 6: Preliminary Impression - Impression Trays
Usually taken with stock trays (metal or plastic, perforated or unperforated).
Trays should be rigid, strong, and retain their dimensions.
Handles should be angulated; stock trays for edentulous mouths have a rounded cross-section.
Page 7: Impression Tray Dimensions
Dimensions are critical:
Too large: distorts tissue and sulcus dimensions.
Too small: collapses tissue inward, affecting border extension.
Edentulous arch should be centered in the tray's reservoir.
Page 8: Tray Selection
Select a tray wider than the existing denture by 3-4 mm on each side.
Page 9: Measuring Distances
Measure with a compass between external surfaces of the tuberosities in the maxilla and retromolar protuberances in the mandible.
Page 10: Maxillary Tray Positioning
Position the tray by centering the labial notch over the labial frenum.
Distal extension should cover to the vibrating line and include tuberosities and soft palate areas.
Page 11: Mandibular Tray Positioning
Extend the tray to capture ascending ramus and all sulci. Also, capture the external oblique line and retromolar protuberances.
Page 12: Adapting Trays
If the stock tray is unsuitable, cover edges with wax for adaptation.
Page 13: Preliminary Impression - Material
Impression material must adhere to the tray, achievable via perforations or adhesives.
For preliminary impressions, high-viscosity materials like alginate or silicone putty are recommended.
Page 14: Impression Taking Technique
Avoid voids by using high-viscous alginate (20% less water).
Smooth material with a wet finger for better detail capture.
Rotate the tray during the seating to reduce air trapping.
Page 15: Impression of Upper Jaw
Patient's Frankfurt horizontal plane should be parallel to the floor; maxilla at clinician's elbow level.
Clinician stands behind the right side of the patient.
Page 16: Impression of Mandibular Jaw
Raise the patient's tongue, insert the tray between the tongue and ridge, then let the patient relax their tongue.
After seating, instruct patient to perform movements like sucking lips inward or moving tongue laterally.
Page 17: Model Preparation
After impressions, disinfect and pour models using Class I plaster.
Ensure plaster is viscous to avoid irregular surfaces during separation from impression.
Page 18: Custom Tray Fabrication
Use tray resins or light-cured resins.
Tray Resins: Brittle but accurate, easy to adjust.
Light-Cure Resins: More accurate, expensive, require adjustment with an acrylic burr.
Page 19: Border Marking in Custom Tray
Mark border of custom tray 2 to 3 mm short of intended denture border.
Relief for frenulums and stress-bearing areas required.
Page 20: Relief in Custom Tray
Prepare space for selective pressure during molding on soft tissues of the alveolar ridge.
Relief can be achieved by adding wax or drilling holes in the tray.
Page 21: Undercut Areas for Custom Tray
Block out undercut areas:
Maxillary Arch: Frenum, buccal surface of tuberosity, rugae.
Mandibular Arch: Mylohyoid ridge, lingual frenulum.
Page 22: Custom Tray Surface Preparation
Cover the cast surface with wax (2mm thick).
Increase wax thickness if tissue attachments are on the residual ridge.
Smoothing edges and polishing preferred for resin material.
Page 23: Finger Rests for Mandibular Tray
Use finger rests to maintain tray position during impression.
Prevents distortion from material being forced into vestibule.
Page 24: Functional Impression
Obtained with a custom tray, which must fit the edentulous ridges.
Made from rigid material (3-4 mm thick) and designed for effective border molding.
Using custom trays provides uniform distribution of impression material and reduces the quantity needed.
Page 25: Impression Techniques
Techniques to record soft tissue shapes vary between minimal displacement and predetermined displacement.
Distinctions include mucostatic (minimal displacement) and mucocompressive (displacing tissues).
Page 26: Types of Impression Techniques
Mucostatic Impression
Mucodynamic Impression
Minimal Pressure Impression
Selective Pressure Impression
Dynamic Impression
Page 27: Mucostatic Impression
Records mucosa under static conditions without distorting soft tissue.
Retention through close adaptation to mucosa in resting position, primarily for edentulous mandibular arches.
Preferred materials: low-viscosity zinc oxide eugenol, alginate, elastomeric materials.
Page 28: Characteristics of Mucostatic Impression
High fluidity allowing for accurate recording of surfaces without displacement.
Good adaptation to mucosa but poor peripheral seal.
Page 29: Limitations of Mucostatic Impression
Inability to perform border molding; relies on surface tension for retention.
Page 30: Mucocompressive and Mucodynamic Technique
Records mucosa in functional conditions for optimal stability during occlusion.
Requires patient to apply occlusal pressures; custom trays are used alongside occlusal rims.
Page 31: Properties of Mucodynamics
Utilizes high-viscosity materials to record mucosa under pressure, enhancing denture stability.
Selective pressure distribution reduces the risk of tissue resorption or damage.
Page 32: Selective Pressure Technique
Combines extended borders with slight pressure on mobile tissues, optimizing stress distribution and adaptability.
High-viscosity materials minimize pressure in non-stress areas, allowing for effective impression.
Page 33: Final Impressions
Denture borders are established using thermoplastic materials in a process called border molding.
Final impressions are made with selected techniques for precise recording of contours.
Page 34: Border Molding Process
Modify impressions through adding or removing material as needed.
Muscular movements can be controlled by the patient or assisted by the dentist.
Page 35: Properties of Border Molding Material
Easy to shape and use.
Maintains form during insertion.
Non-adherent before molding.
Acceptable setting times (3-5 min).
Can be repaired and excess easily removed.
Stable until impression pouring.
Page 36: Material Types for Border Molding
Thermoplastic compound is commonly used; also waxes and silicone can be utilized.
Offers adjustability and is cost-effective.
Page 37: Functional Compound
Isofunctional compound is ideal for muscle trimming and rebasing, noted for its ease of use and working time.
More expensive than traditional compounds but advantageous.
Page 38: Tray Checking Process
Evaluate all tray borders and sealing areas before use.
Page 39: Softening of Impression Compound
Compound can be softened for shaping before insertion.
Page 40
Discipline is wisdom and vice versa.
M. Scott Peck
THANK YOU FOR LISTENING
Questions: FGULENER@BIRUNI.EDU.TR